Seal for a rotary valve for an internal combustion engine

ABSTRACT

A gas seal between a port ( 10, 12 ) of a rotary valve ( 7 ) and a port ( 8 ) in a combustion chamber ( 6 ) of a rotary valve engine, the seal comprising gas channel means ( 15 ) forming a turbo valve means ( 26 ) surrounding the port ( 8 ) in the combustion chamber and compression means ( 20, 21 ) for creating a pressure in the gas channel means greater than a pressure in the combustion chamber during a compression stroke and a power stroke of the engine.

This invention relates to a seal for a rotary valve for an internalcombustion engine.

Known commercially available internal combustion engines have changedlittle in principle since their invention in 1892. Although there havebeen many variations of engine, they have all used similar principles.

A known four-stroke engine includes a cylinder block comprising at leastone cylinder bore in which a piston may reciprocate, a crankcaserotatably supporting a crankshaft connected to the piston via a con rodand a cylinder head containing a valve mechanism comprising an inletvalve and an outlet valve opening to the cylinder bore. As thecrankshaft rotates, the piston reciprocates within the cylinder bore.Rotation of the crankshaft also causes rotation of a camshaft within thecylinder head that, using one of a variety of mechanisms, opens andcloses the inlet and outlet valves in the cylinder head.

On an induction or intake stroke, the piston travels along the cylinderbore in a direction away from the valve mechanism with the inlet valveopen. A partial vacuum created in a combustion chamber within thecylinder bore between the piston and the valve mechanism draws a mixtureof vaporised fuel and air into the cylinder bore from, for example, acarburettor.

On a return stroke the piston travels back along the cylinder boretowards the valve mechanism with the inlet valve now closed, compressinggas within the combustion chamber between the piston and an end of thebore at which the inlet and outlet valves are located.

As the piston reaches an end of its reciprocating motion along thecylinder bore towards the inlet and outlet valves, ignition takes placeigniting the compressed fuel and air mixture. This generates a powerstroke pushing the piston in a direction away from the valve mechanism,in turn rotating the crankshaft.

The piston then travels back towards the valve mechanism and in turn theexhaust valve opens, so that hot exhaust gases are forced out of thecylinder and cylinder head, and exit the engine via an exhaust gas path.

The four-stroke engine requires many components to operate the valvesystem within the cylinder head. These components increase a cost of theengine. The engine may also emit a high level of noxious gases in itsexhaust fumes.

Over the years, as more appropriate materials have become available,higher performance engines have been manufactured resulting in higherspeeds and reliability. However, there have been few attempts to produceother types of internal combustion engine, and the most commonalternative that has become commercially established is a two-strokeengine. The two-stroke engine differs from the more common four-strokeengine by completing the same four processes (intake, compression,power, exhaust) in only two strokes of the piston rather than four. Thisis accomplished by using the beginning of the compression stroke and theend of the power stroke to perform the exhaust and intake functions,respectively. This allows a power stroke for every revolution of thecrank, instead of every second revolution as in a four-stroke engine.For this reason, two-stroke engines provide high specific power, so theyare valued for use in portable, lightweight applications.

However, proposals to replace the valves and con rods of a conventionalinternal combustion engine with a rotary valve for supplying gas to, andexhausting gas from, a cylinder of an internal combustion engine arealso well know.

U.S. Pat. No. 4,852,532 discloses a rotary valve for an internalcombustion engine having a hollow cylindrical rotor with an inclinedintegral baffle along its bore with ports on either side of the bafflearranged to be brought into communication with a window in the cylinderas the hollow cylindrical rotor rotates. The rotor is supported byrollers supported in grooves formed in a surface of the rotor andbearing on the inside surface of a bore of the cylinder head. Seals areprovided around the window, the seals consisting of sealing stripsarranged in longitudinal grooves formed in the bore of the cylinder headand circumferential rings accommodated in annular grooves within thebore of the cylinder head. The longitudinal strips abut in surfacecontact at each end of the surface of one of the circumferential rings.Passages are provided in the cylinder head for cooling water and in therotor for cooling oil. Cooling of the rotor is accomplished by radiationto an adjacent surface of the rotor bore which is cooled by water in thewater passages and by a flow of oil in the oil passage.

GB 2234300 discloses an air-cooled rotary valve including within thecylindrical rotary valve an inlet duct communicating with an inlet portopening into the cylinder when aligned with the cylinder and an exhaustduct communicating with an exhaust port circumferentially offset fromthe inlet port, opening into the cylinder when aligned with thecylinder. Two circumferential grooves containing sealing rings arelocated one on each side of the inlet and outlet ports to isolate theports from the environment. Longitudinal sealing bars are provided toisolate the inlet port from the outlet port. The rotary valve is cooledby passing air through a bore of the rotary valve.

U.S. Pat. No. 5,941,206 discloses a rotary valve for an internalcombustion engine, comprising a cylindrical valve rotor having an inletand an outlet port in a circumferential surface. A plurality of sealingelements mounted on the valve rotor divide the circumferential surfaceof the rotor body to define discrete circumferential surface zones. Oneof the zones is arranged so that, when the rotary valve is receivedwithin a valve bore in a cylinder head, the sealing elements abut on thevalve bore surface and the ports are periodically sealed off.

WO 02/27165 discloses a rotating valve engine with an engine housingthat contains an annular timing ring, a rotatable cylinder with a closedend and an open end; and a piston within the cylinder. The cylinder ismechanically driven by the piston via a transmission assembly thatincludes a con rod that drives a gear that in turn engages a bevel gearformed at the open end of the cylinder. The rotating valve is cooled byoil forced over the rotating cylinder.

U.S. 2004/0144361 discloses a rotary valve internal combustion engineincluding a crankshaft, a throttle, a throttle actuator, a cylinderhead, a combustion chamber, and at least one rotary valve. The rotaryvalve has at least two ports terminating as openings in its periphery,the cylinder head having a bore in which the rotary valve rotates. Awindow in the bore communicates with the combustion chamber, theopenings successively aligning with the window by virtue of therotation. A drive mechanism with phase change means drives the rotaryvalve. The ports comprise an inlet port and an exhaust port, and thephase change means applies a phase change in response to changes in theoperating conditions of the engine over at least one engine cycle.

A particular concern in rotary valve engines has been to find means ofsealing the valve ports of the rotating valve against leakage underpressure.

U.S. Pat. No. 5,526,780 discloses a rotary valve assembly for aninternal combustion engine in which the valve has a combination of axialsealing elements and inner circumferential sealing elements arranged toform a first seal pressurizing cavity extending circumferentiallybetween the axial sealing elements and two second seal pressurizingcavities each lying between the inner and adjacent outer circumferentialsealing elements axially on each side of a window opening in a cylinderhead in which the valve rotates. The arrangement permits high pressurecombustion gas to pass from the first cavity to the two second cavitieswhereby during combustion the outer circumferential sealing elements arecaused to seal the second pressurizing cavities by being forced againstthe axially outermost sides of circumferentially extending grooves inwhich they are located to prevent axially outward movement of gas. Theinner circumferential sealing elements are loaded axially inwardly toseal against axially innermost sides of circumferentially extendinggrooves in which they are located and to load the four circumferentialsealing elements radially to seal against a bore surface in which thevalve is housed and against which they are preloaded.

WO 03/100232 discloses a valve seal mechanism for a rotatable valveassembly that provides a seal between a rotating valve element and afixed valve element as used in a rotary cylinder valve engine. In oneembodiment the seal mechanism comprises a substantially rigid sealingframe which surrounds and seals the periphery of the valve port of oneof the cylindrical valve elements and also seals a surface of the othercylindrical valve element. In another embodiment, the seal mechanismcomprises a resiliently deflectable tubular element of variablediameter, mounted around a first valve element with an aperture of thetubular element being radially aligned with a valve port of the firstvalve element, the tubular element being biased radially outward of thefirst valve element. Cooling of the valve and the sealing mechanism iseffected by pumping cooling fluid through coolant channels in a housingof the valve and then over lower parts of the rotating valve element.

WO 2005/119018 discloses a seal arrangement for a rotary valve internalcombustion engine having a cylinder including a valve port incommunication with a combustion chamber. The cylinder is rotatable aboutits longitudinal axis in a cylindrical bore of a valve housing, thevalve housing having an inlet port and an outlet port adapted to bealigned successively with said valve port during rotation of thecylinder in the housing to enable fluid to flow respectively into andout of the combustion chamber. A seal is provided around the valve portbetween the cylinder and a concentric surface, and comprises a sealelement located in a recess in the cylinder, fluid pressure in saidvalve port acting on said seal element to urge the seal element intocontact with the concentric surface and outwardly from the centre of theport into contact with the periphery of the recess.

WO 2006/024081 discloses a sealing system for an axial flow rotary valveinternal combustion engine comprising an array of floating gas seals andan optional oil sealing system. The array of floating seals surrounds awindow in the bore of the cylinder head through which the ports of thevalve communicate with a combustion chamber. The array of floating sealscomprises axial seals and circumferential seals housed in slots in thebore of the cylinder head wherein the circumferential seals are disposedaxially between the ends of the axial seals. The valve may be cooledwith oil that is pumped through the valve.

WO 2006/024086 discloses an axial flow rotary valve for an internalcombustion engine comprising a cylinder head having a bore in which anaxial flow rotary valve rotates. The valve has a cylindrical centreportion, and an inlet and an exhaust port terminating as openings in thecentre portion. The openings periodically communicate with a combustionchamber through a window in the bore. A clearance between the centreportion and the bore is sealed by an array of floating seals comprisingat least two axial seals spaced apart on opposite sides of the window.The assembly further comprising at least one floating axially extendingmasking seal being disposed outside the window and circumferentiallyremote from the axial seals. In some instances the valve is cooled withoil that is pumped through the valve.

It is therefore apparent that only complex mechanical arrangements areknown for sealing ports of a rotary valve against leakage in an axialdirection under pressure.

It is an object of the present invention at least to ameliorate theaforesaid deficiency in the prior art.

According to the invention, there is provided a gas seal system betweena port of a rotary valve and a port in a combustion chamber of a rotaryvalve engine, the seal comprising gas channel means forming a turbovalve means surrounding the combustion chamber port and compressionmeans for creating a pressure in the gas channel means greater than apressure in the combustion chamber during a compression stroke and apower stroke of the engine.

Advantageously, a clearance between the turbo valve means and an outersurface of the rotary valve is approximately 0.0254 mm (1 mil).

Conveniently, the compression means comprises a turbo valve injectormeans for injecting gas substantially tangentially into the turbo valvemeans.

Conveniently, the gas seal system further comprises position sensormeans for sensing a rotational position of a rotor of the rotary valvefor signaling to the compression means.

Conveniently, the gas seal system further comprises valve means forcontrolling admission of compressed gas from the compression means tothe turbo valve injector means on receipt of signals from the sensormeans.

Advantageously, the compression means comprises a compression chambermeans.

Conveniently, the compression means comprises compressor means driven bya crankshaft of the rotary valve engine.

Alternatively, the compression means comprises a crankcase of the enginepressurised by intake and power strokes of the engine.

Conveniently, the crankcase comprises a one-way valve means foradmitting air into the crankcase on compression and exhaust strokes ofthe engine.

Conveniently, the gas seal system further comprises a non-return valvemeans for passing compressed air from the crankcase to the compressionchamber means.

According to a second aspect of the invention, there is provided arotary valve engine comprising a gas seal as described above.

Conveniently, a rotor of the rotary valve is arranged to be cooled bypassing water through a bore of the rotor.

According to a third aspect of the invention, there is provided a methodof providing a seal in a rotary valve engine between a port in therotary valve and a port in a combustion chamber of the engine,comprising the steps of: providing a gas channel means forming a turbovalve means surrounding the combustion chamber port; creating, with gascompression means, a pressure in the gas channel means greater than apressure in the combustion chamber during a compression stroke and apower stroke of the engine.

Conveniently, the method further comprises injecting gas substantiallytangentially into the turbo valve means with a turbo valve injectormeans.

Conveniently, the method further comprises sensing a rotational positionof a rotor of the rotary valve with sensor means for signaling to thecompression means.

Conveniently, the method further comprises controlling admission ofcompressed gas from the compression means to the turbo valve injectormeans on receipt of signals from the sensor means.

Advantageously, creating a pressure in the gas channel means comprisescreating a pressure in a compression chamber means.

Conveniently, creating a pressure in the gas channel means comprisescreating a pressure with a compressor means driven by a crankshaft ofthe rotary valve engine.

Alternatively, creating a pressure in the gas channel means comprisespressurising air in a crankcase of the engine by intake and powerstrokes of the engine.

Conveniently, pressurising air in the crankcase, comprises admitting airinto the crankcase through a one-way valve means on compression andexhaust strokes of the engine.

Conveniently, creating a pressure in the gas channel means comprisespassing compressed air from the crankcase to the compression chambermeans through pneumatic tubing means and a non-return valve means.

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 is a cut away drawing of a rotary valve internal combustionengine according to the invention;

FIG. 2 is a vertical, longitudinal cross-section of the engine of FIG.1;

FIG. 3 is a side view of the engine of FIG. 1;

FIG. 4 is a front view of the engine of FIG. 1;

FIG. 5 is a rear view of the engine of FIG. 1;

FIG. 6 is a front view of the engine of FIG. 1, including a gascompression system;

FIG. 7 is a vertical, transverse cross-section of the engine of FIG. 6;

FIG. 8 is a vertical, transverse cross-section of a gas seal of theengine of FIG. 6; and

FIG. 9 is a plan view of the gas seal of FIG. 8.

In the Figures, like reference numerals denote like parts.

Referring to FIGS. 1 to 3 and 7, a rotary valve engine comprises a onepiece cylinder block 1 and cylinder head 2, eliminating cylinder headbolts and a cylinder head gasket, which are required in a standardinternal combustion engine to join a separate cylinder block andcylinder head, which in a water-cooled engine can be a source of waterleaks. The one-piece construction also provides a more rigidconstruction than that of a standard internal combustion engine. Thecylinder block 1 is provided with a conventional crankshaft 3, con rods4, and pistons 5. Referring to the orientation of the engine in thedrawings, within the cylinder head 2 and just above combustion chambers6 above the pistons 5 there is a rotary valve 7 which controls inlet andexhaust gases going in and out of the combustion chambers 6,respectively, via ports 8 in upper ends of the combustion chambers 6.

The rotary valve 7 is driven by the crankshaft 3 using a toothed belt 9at a front of the engine accurately to align inlet ports 10 and exhaustports 12 within the circumference of the rotary valve 7 with the ports 8with the same accurate precision as provided by cams and mechanicalmechanisms in opening and closing valves in a standard internalcombustion engine. As a piston 5 travels down the cylinder block 1within a bore of a cylinder 11, a port 10 within the rotary valve 7rotates to a position over the cylinder head port 8, allowing inletgases to be drawn into the combustion chamber 6.

As the piston 5 rises up the cylinder 11 in the cylinder bore on acompression stroke, the rotor 7 continues to rotate and blanks off theport 8 in the cylinder head 2. The compressed charge is then ignited,for example by a spark plug, resulting in a power stroke while the rotor7 continues to rotate.

As the piston 5 rises up the cylinder again on an exhaust stroke toforce out exhaust gases, an exhaust port 12 within the rotor 7 reachesthe port 8 within the cylinder head 2, allowing the exhaust gases to bepurged out of the engine through the rotary valve. This process iscarried out within the engine; each cylinder having its own set of inletand outlet ports within the rotary valve 7.

The rotor of the rotary valve 7 is water-cooled in a more efficientmanner than cooling in a conventional cylinder head. Also the surface 16of the rotor 7 that passes over the cylinder head port 8 absorbs theheat over a relatively large area compared with heat exchange surfacesin a conventional engine. Water enters the rotor 7 at a front end 13 ofthe cylinder block and exits at a rear end 14 into the cylinder block 1.This ensures that maximum desirable cooling is given to the rotor 7. Therotor 7 is a one piece structure that may be constructed to fitlengthways over any number of cylinders as a one piece component, sothat water can enter at one end and exit through the other end, unlikesome previous rotary valves where inlet and exhaust gases have had touse either end for transfer, making them only suitable for singlecylinder engines without any water cooling.

An advantage of the rotary valve of the present invention is that theinlet and the exhaust valves are shaped to act as a conventional port ofa standard engine, allowing the gasses to enter and leave through a sideof the rotor. This means that the inlet gas for the cylinder orcylinders can enter the rotor across to the centre of the rotor, andthen turn downwards into the cylinder.

After combustion has taken place, the exhaust port in the rotor opens,allowing the exhaust gas to enter the port and to be forced across acentre of the rotor and out through the side of the rotor and throughthe cylinder head port to an exhaust pipe.

This allows water to enter the front of the rotor and have a clearpassage around each of the ports mounted across the rotor from side toside.

Control of thermal expansion of the rotor is easily achieved to maintaina running clearance with the cylinder head.

Referring to FIG. 4, the exhaust port 12 has an angled leading edge 17,as best seen in FIG. 6, which shaves carbon build up off the cylinderhead surface 18 ensuring a maximum sealing of combustion pressure,minimizing an air pressure required in a recess groove 15, describedbelow, to ensure complete sealing throughout the working life of theengine.

Referring to FIGS. 1 and 7 to 9, to maintain compression of inlet gaseswithin the cylinder head 2, a recess groove 15 is provided whichencircles the port 8 on an outer face of an upper end of the cylinderand is linked to air channels, as best seen in FIG. 8, to form a turbovalve 26. Air is supplied under pressure to the turbo valve 26. The aircan be supplied by a small compressor, not shown, driven by thecrankshaft 3 or, as illustrated in FIG. 6, the required pressure isgenerated internally by the pistons 5 of the engine.

As the piston 5 ascends, a valve, not shown, in the side of thecrankcase 19, automatically opens to atmosphere, allowing air to bedrawn into the crankcase. As the piston 5 descends on a power stroke ofthe engine, the crankcase valve closes and the piston compresses airwithin the crankcase 19 forcing air through pneumatic tubing and anon-return valve 20 into an air storage chamber 21. On a multi-cylinderengine, the crankcase has dividing walls, not shown, either cast as partof the crankcase or fitted separately to provide individual compartmentsfitted with an oil seal at the crankshaft main bearing. This is to alloweach compartment to work with a respective air valve system activated bythe downward stroke and the upward stroke of the piston within thatrespective compartment individually.

This charging of the air storage chamber occurs twice per power strokeof the engine, providing the air storage chamber 21 with a volume ofcompressed air. As the piston 5 of the engine ascends under compressionfor its power stroke a solenoid valve 22 is triggered into operation bya sensor 23 operated by the rotor 7 in the cylinder head 2 to allow airto be led from the air storage chamber 21 via a pneumatic tubing system24 and the electronic solenoid valve 22 to a turbo valve injector 25which forces the compressed air substantially tangentially into thecircular groove 15, as best seen in FIG. 9, to circulate at high speedaround the recess groove 15 of the turbo valve 26. The turbo valve 26 islocated at an upper end of the combustion chamber 6 and is only 0.0254mm (1/1,000^(th) of an inch) clear of the circumference 16 of rotor 7.

An upper portion of a wall of the turbo valve 26, with a profileconforming to an outer circumference of the rotor 7 radius, has achamfer 27. This concentrates the air pressure on the 0.0254 mm (1/1,000inch) gap 28 between an upper edge of the turbo valve and a surface ofthe rotor 7.

The pressure of the circulating air in the gap 28 between the turbovalve and rotor surface is arranged to be greater than the gas pressureinside the combustion chamber 6 so that all fuel and detonationcombustion gases are retained in the combustion chamber 6 during thecompression and power strokes respectively.

This external air pressure is held in the turbo valve 26 during thecombustion stroke and the exhaust stroke of the engine. As the exhaustport 10 within the rotor 7 moves to a location over the port 8 to allowthe exhaust gases to escape, the sensor 23 receives a pulse from therotor 7 and sends a signal which causes the electronic solenoid valve 22to close. At the same time, the compressed air around the turbo valve 26escapes through the port 10 which cools the exhaust gas on its way tothe atmosphere.

A conventional engine will emit a high level of poisonous gases into theatmosphere. This is because the exhaust valves run red hot, superheatinggases passing through them. As the engine of the invention runs a lotcooler and does not have those problems, the exhaust gases the engineemits produces reduced pollution of the atmosphere compared withconventional internal combustion engines.

It will be understood that the electronic solenoid valve 22 can bereplaced by, for example, a mechanical cam driven valve.

DRAWING COMPONENT NUMBERS

-   (1) Cylinder block-   (2) Cylinder head-   (3) Crankshaft-   (4) Conrod-   (5) Piston-   (6) Combustion chamber-   (7) Rotor-   (8) Combustion chamber port-   (9) Toothed belt-   (10) Inlet port-   (11) Cylinder-   (12) Exhaust port-   (13) Front end-   (14) Back end-   (15) Recess groove-   (16) Rotor surface-   (17) Angled trailing edge-   (19) Crankcase-   (20) Non return valve-   (21) Storage chamber-   (22) Solenoid valve-   (23) Sensor-   (24) Pneumatic tubing system-   (25) Turbo valve injector-   (26) Turbo valve-   (27) Chamfer-   (28) Gap between upper edge of turbo valve and rotor

1. A gas seal system between a port of a rotary valve and a port in acombustion chamber of a rotary valve engine, the seal comprising gaschannel means forming a turbo valve means surrounding the combustionchamber port and compression means for creating a pressure in the gaschannel means greater than a pressure in the combustion chamber during acompression stroke and a power stroke of the engine.
 2. A gas sealsystem as claimed in claim 1 wherein a clearance between the turbo valvemeans and an outer surface of the rotary valve is approximately 00254 mm(1 mil).
 3. A gas seal system as claimed in claim 1, wherein thecompression means comprises a turbo valve injector means for injectinggas substantially tangentially into the turbo valve means.
 4. A gas sealsystem as claimed in claim 3, comprising position sensor means forsensing a rotational position of a rotor of the rotary valve forsignaling to the compression means.
 5. A gas seal system as claimed inclaim 4, comprising valve means for controlling admission of compressedgas from the compression means to the turbo valve injector means onreceipt of signals from the sensor means.
 6. A gas seal system asclaimed in claim 1, wherein the compression means comprises acompression chamber means.
 7. A gas seal system as claimed claim 1,wherein the compression means comprises compressor means driven by acrankshaft of the rotary valve engine.
 8. A gas seal system as claimedin claim 1, wherein the compression means comprises a crankcase of theengine pressurised by intake and power strokes of the engine.
 9. A gasseal system as claimed in claim 8, wherein the crankcase comprises aone-way valve means for admitting air into the crankcase on compressionand exhaust strokes of the engine.
 10. A gas seal system as claimed inclaims 8, comprising a non-return valve means for passing compressed airfrom the crankcase to the compression chamber means.
 11. A rotary valveengine comprising a gas seal as claimed in claim
 1. 12. A rotary valveengine as claimed in claim 11, wherein a rotor of the rotary valve isarranged to be cooled by passing water through a bore of the rotor. 13.A method of providing a seal in a rotary valve engine between a port inthe rotary valve and a port in a combustion chamber of the engine,comprising the steps of: a. providing a gas channel means forming aturbo valve means surrounding the combustion chamber port; b. creating,with gas compression means, a pressure in the gas channel means greaterthan a pressure in the combustion chamber during a compression strokeand a power stroke of the engine.
 14. A method as claimed in claim 13,comprising injecting gas substantially tangentially into the turbo valvemeans with a turbo valve injector means.
 15. A method as claimed inclaims 13, comprising sensing a rotational position of a rotor of therotary valve with sensor means for signaling to the compression means.16. A method as claimed in claim 14, comprising controlling admission ofcompressed gas from the compression means to the turbo valve injectormeans on receipt of signals from the sensor means.
 17. A method asclaimed in claim 13, wherein creating a pressure in the gas channelmeans comprises creating a pressure in a compression chamber means. 18.A method as claimed in claim 13, wherein creating a pressure in the gaschannel means comprises creating a pressure with a compressor meansdriven by a crankshaft of the rotary valve engine.
 19. A method asclaimed in claim 13, wherein creating a pressure in the gas channelmeans comprises pressurising air in a crankcase of the engine by intakeand power strokes of the engine.
 20. A method as claimed in claim 19,wherein pressurising air in the crankcase, comprises admitting air intothe crankcase through a one-way valve means on compression and exhauststrokes of the engine.
 21. A method as claimed in claim 17, whereincreating a pressure in the gas channel means comprises passingcompressed air from the crankcase to the compression chamber meansthrough pneumatic tubing means and a non-return valve means.